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Fix a bug when a migration is followed by a rebalance

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Nodes would stabilize on different encoding formats for the values,
some having the pre-migration format and some having the post-migration
format. This would be reflected in the Merkle trees never converging
and thus having an infinite resync loop.
This commit is contained in:
Alex Auvolat 2022-02-10 12:33:29 +01:00 committed by Gitea
parent 4ae03aa774
commit af261e1789
1 changed files with 18 additions and 9 deletions
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21
src/table/data.rs
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@ -130,22 +130,31 @@ where
let tree_key = self.tree_key(update.partition_key(), update.sort_key());
let changed = (&self.store, &self.merkle_todo).transaction(|(store, mkl_todo)| {
let (old_entry, new_entry) = match store.get(&tree_key)? {
Some(prev_bytes) => {
let (old_entry, old_bytes, new_entry) = match store.get(&tree_key)? {
Some(old_bytes) => {
let old_entry = self
.decode_entry(&prev_bytes)
.decode_entry(&old_bytes)
.map_err(sled::transaction::ConflictableTransactionError::Abort)?;
let mut new_entry = old_entry.clone();
new_entry.merge(&update);
(Some(old_entry), new_entry)
(Some(old_entry), Some(old_bytes), new_entry)
}
None => (None, update.clone()),
None => (None, None, update.clone()),
};
if Some(&new_entry) != old_entry.as_ref() {
// Scenario 1: the value changed, so of course there is a change
let value_changed = Some(&new_entry) != old_entry.as_ref();
// Scenario 2: the value didn't change but due to a migration in the
// data format, the messagepack encoding changed. In this case
// we have to write the migrated value in the table and update
// the associated Merkle tree entry.
let new_bytes = rmp_to_vec_all_named(&new_entry)
.map_err(Error::RmpEncode)
.map_err(sled::transaction::ConflictableTransactionError::Abort)?;
let encoding_changed = Some(&new_bytes[..]) != old_bytes.as_ref().map(|x| &x[..]);
if value_changed || encoding_changed {
let new_bytes_hash = blake2sum(&new_bytes[..]);
mkl_todo.insert(tree_key.clone(), new_bytes_hash.as_slice())?;
store.insert(tree_key.clone(), new_bytes)?;